1. Field
The present disclosure relates to a power supply apparatus able to control an output current and a power supply method using the same, and more particularly, to a power supply apparatus able to control an output current providing power so as to maintain plasma in a plasma generator in a field of generating a reaction gas including ions, free radicals, atoms, and molecules, and a power supply method using the same.
2. Description of Related Art
Plasma discharge may be used to excite a gas to generate a reaction gas including ions, free radicals, atoms, and molecules. The reaction gas is used in numerous industrial and scientific applications including an application of processing a solid material such as a semiconductor wafer, powders, and other gases. A plasma state means a state in which a gas is ionized when high energy is given to the gas, and a plasma generating apparatus has been used in an etching process, a cleaning process, and the like, of processes of manufacturing a semiconductor in the modern times and the importance of the plasma generating apparatus has gradually increased in accordance with the growth of a semiconductor market.
Generally, several processes for manufacturing the semiconductor are performed in a semiconductor process, and byproducts generated in the semiconductor process are exhausted through a vacuum pump and a scrubber. In this case, a fine organic contaminant, oxide, or the like, generated in the semiconductor process is effectively removed using plasma.
There is a method of generating the plasma inside a process chamber or generating the plasma outside a process chamber. Here, as the method of generating the plasma outside a process chamber, there is a method of using a remote plasma generator. The remote plasma generator is an equipment of applying a high electric field to a neutral gas (argon) to separate some of the neutral gas into protons and electrons and generate plasma in which the neutral gas, the electrons, and the protons are mixed with one another by energy of the electric field.
A plasma supply source for the remote plasma generator may generate the plasma in various manners including direct current (DC) discharge, radio frequency (RF) discharge, and microwave discharge. The DC discharge is accomplished by applying a potential between two electrodes in the gas. The RF discharge is accomplished by transferring energy from a power supply into the plasma in a static electricity manner or an induction coupling manner. An induction coil is generally used to induce a current into the plasma. The microwave discharge is accomplished by directly coupling microwave energy into a discharge chamber accommodating a gas therein. The microwave discharge may be used to support a wide discharge condition including heavily ionized electron cyclone resonance (ECR) plasma.
A toroidal plasma supply source has advantages in terms of a lower electric field, low corrosion of a plasma chamber, miniaturization, and a cost effect as compared with a microwave plasma supply source or another type of RF plasma supply source. The toroidal plasma supply source generates plasma in an inductively coupled plasma (ICP) manner. A toroidal plasma generator has been used to chemically generate an active gas including fluorine, oxygen, hydrogen, nitrogen, or the like, in order to process a semiconductor wafer, a flat panel display, and various materials.
A gas supplied through a gas inlet of the toroidal plasma supply source moves along a toroidal plasma channel in the plasma chamber, and reacts to the plasma to generate an activated gas. A flow of the gas in the plasma chamber acts as impedance.
A predetermined level or more of energy is required in order to maintain the plasma state generated as described above. The toroidal plasma supply source using the ICP manner uses a magnetic field in order to supply energy to the gas, and supplies a current having a high frequency to a plasma generator in order to generate such a magnetic field. In the case in which a magnitude of such a current is reduced, it is difficult to maintain the gas in the plasma state, and the gas that is not maintained in the plasma state does not act as a load, but shows electrical resistance having an open form such as the atmosphere. A phenomenon that the predetermined level or more of energy is not supplied to the gas, such that the plasma is not maintained is called a drop-out phenomenon. After the plasma is ignited, an electrical resistance value is in an inverse proportion to a current applied to the plasma generator. Due to such a feature, in the case of using a resonant power supply apparatus in a plasma load, the drop-out phenomenon occurs.
In the case in which the drop-out phenomenon occurs, a problem occurs in processes such as the etching process, the cleaning process, and the like, of the processes of manufacturing a semiconductor, and the plasma generating apparatus should be restarted, such that temporal loss exists.
FIG. 1 is a view showing characteristics when plasma is operated as a load of a power supply apparatus after plasma is ignited, and FIG. 2 is a circuit diagram illustrating a resonance network according to the related art and a resonance network of a plasma generator.
Referring to FIG. 1, after plasma is ignited, a plasma load has an electrical resistance value that is in inverse proportion to a change in a current. In the case in which the power supply apparatus controls a current to be reduced through a frequency variation, an electrical resistance value of the plasma is increased depending on the reduced current. Therefore, an output current is reduced once again. A process in which the electrical resistance value of the plasma load is again increased by the reduced output current is repeated, such that the plasma load returns to an air form such as before the plasma is ignited. Therefore, there is a difficulty in controlling the output current by a general frequency control.
Referring to FIG. 2, currently, as a power supply apparatus for generating and maintaining the plasma, a resonant power supply apparatus easily outputting a constant current is used in order to generate and maintain the plasma even in a rapid resistance change condition before or after the plasma is ignited and generate a high frequency power required in the plasma. To this end, an LC parallel resonant network 1 is used. The resonant network 1 includes a resonance inductor 3 connected to a plasma generator 5 in series and a resonance capacitor 4 connected to the plasma generator 5 in parallel.
As the power supply apparatus for generating and maintaining the plasma, the resonant power supply apparatus easily outputting the constant current is used in order to generate and maintain the plasma even in the rapid resistance change condition before or after the plasma is ignited and generate the high frequency power required in the plasma. In such a system, a frequency variation is required in order to vary an output current.
In the resonant power supply apparatus, in the case of a general load, an impedance change of the load about an increase or a decrease in a current does not exist and an influence on a change in a Q-factor is low, but in the case of a plasma load, a series of changes in a Q-factor are generated due to an impedance change for an increase or a decrease in a current, such that it is difficult to obtain an output by a general frequency control. Particularly, conventionally, in operating the plasma generator after the plasma is ignited, the power supply apparatus was designed without considering the drop-out phenomenon, and thus performed only a current control through a frequency variation.